1. Field of the Invention
This invention relates to a packaged semiconductor device of the type which incorporates a heat sink plate for effectively dissipating the heat generated by a semiconductor chip. The present invention also relates to a method for making such a semiconductor device. The present invention further relates to supersonic bonding which can be advantageously used in making such a semiconductor device.
2. Description of the Related Art
As is well known, certain types of semiconductor devices generate a lot of heat during operation. For example, power ICs for motor drive, certain gate array devices and ultra LSIs are known to generate much heat. Therefore, these semiconductor devices equally need to incorporate a heat sink plate within the resin package for effectively dissipating the generated heat, as shown in FIG. 36 of the accompanying drawings.
Specifically, as shown in FIG. 36, a prior art packaged semiconductor device of this type comprises a semiconductor chip 5 mounted on a heat sink plate 4 within a resin package 1. The chip 5 is electrically connected to a plurality of leads 2 via respective bondwires 6. An inner portion of each lead 2 is attached to the heat sink plate a via an adhesive layer 3, whereas an outer portion of the lead 2 is extended out of the package 1. In operation, the heat sink plate 4 serves to dissipate heat which is generated by the semiconductor chip.
However, the prior art semiconductor device has been found to have the following disadvantages.
First, before molding the resin package 1 in manufacturing the prior art semiconductor device, the heat sink plate 4 need be supported solely by the tip ends of the respective leads 2 via the adhesive layer 3. Since the leads 2 need be extremely slenderized for enabling a dense arrangement in a limited size, they cannot provide a sufficiently rigid support if the heat sink plate 4 is rendered relatively heavy. Therefore, it is difficult to increase the heat dissipating ability of the heat sink plate 4 beyond a certain limit.
Secondly, in bonding the bondwires 6 to the respective leads 2 before molding the resin package 1, the heat sink plate 4 need be placed on a heater block (not shown) to supply heat required for performing a thermo-compression bonding method. However, since the adhesive layer 3 blocks heat transmission from the heat sink plate 4 to each lead 2, it is difficult to properly and efficiently bond the wire 6 to the lead 2.